1. Field of the Invention
The present invention pertains generally, to devices for investigation of physicochemical properties of materials and articles, in particular to devices for investigation of the structure of porous bodies.
2. Description of Related Art Including Information Disclosed Under 37 CFR 1.97 and 1.98
Devices for investigation of the porous structure of samples are known.
Generally, they employ a method of nonwettable liquid intrusion into pores of a test sample namely mercury, and are known as mercury porosimeters (H. L. Ritter, L. C. Drake, Ind. Eng. Chem. Analit. Ed., 17, 787, 1945; SU Inventors Certificate No. 104315, 1952 G 01 (15/08).
The mercury porosimeters, which are the most widespread porosimetric devices, measure distribution of pores by the samples' radii within the pore size range from 2 to 10.sup.5 nm.
However, measurements accomplished within the pore-size range from 2 to 7 nm require applying very high pressure to intrude mercury into the samples pores which is up to 4000 ATM and which involves a complicated device.
Under pressures of thousands ATM, deformation and destruction of most samples measured, especially plastic ones, takes place.
Besides, it is impossible to use mercury porosimeters for investigation of substances, which chemically react with mercury (amalgamation).
Also, when mercury porosimeters are used, the value of angle of wetting by mercury for most of the samples measured is not known. However, this value is used for computation of radii of pores measured.
In practice, various materials are measured when some mean value of this angle of wetting issued which entails significant errors in measurement.
Of great importance when employing mercury porosimeters is that it uses a substantial quantity of a highly toxic substance-mercury.
Also known in the art are devices for measurement of the porous structure of a substance by means of a method of capillary condensation, for instance an adsorption apparatus (A. W. Adamson, Physical Chemistry of Surface, John Wiley & Sons Publ., New York, 1976).
However, devices operating by the capillary condensation method provide sufficient accurate measurement of distribution of pores by radii only within the range from 1 (or -2) to 50 nm.
Also known is a device for measurement of characteristics of porous bodies by the method of standard porosimetry (USSR Inventor's Certificate No. 543852, 1975, GO1N15/08, Yu. M. Volfkovich, V. S. Bagotzky, J. Power Sources, 48 (1994) 327, 339).
The method is based on the fact that when pores of the test sample are filled with a wetting liquid or are free of the liquid, and when a determination of a quantity of liquid contained in its pores takes place, the test sample is brought into contact with the standard porous sample and when capillary equilibrium is achieved a measurement is performed of the quantity of the liquid in the test and standard samples.
The method consists in measurement, performed in the course of drying, of equilibrium dependency of a quantity of liquid in the test sample from its quantity in the standard sample while the samples are in contact with each other.
Proceeding from a curve plotted against results of measurements also from a known curve of distribution of pores by radii (porosimetric curve) for standard samples, it is determined under a specific procedure, porosimetric curves for the test samples.
By means of a mathematical processing of these curves other characteristics of a porous structure are obtained, for instance a specific surface.
A quantity of liquid in each porous sample is determined by means of weighing in the course of drying.
A device for measurement of the standard porosimetery consists of scales and a clamping device, wherein the test and standard porous samples are brought into contact.
The clamping device represents a body arranged as a beaker where the porous test and standard samples are placed. The samples are shut down by means of a draw plate having apertures through which drying of a stack is performed. A throw nut screwed on the body of the device clamps the samples to each other. To get one point on the porosimetric curve the stack is disassembled, the porous samples from the stack are laid out into individual bottles, and then after weighting, all samples are removed from the bottles, and the stack is reassembled anew in the clamping device. Then the next portion of the liquid is evaporated from the stack through drying, by means of a flow of dry gas or by vacuum, after which the stack of the porous bodies is disassembled, the porous bodies are laid out anew into the individual bottles, and then are weighed again.
To measure one porosimetric curve it is necessary depending on the required accuracy of measurement, to conduct this cycle of operations from fifteen up to fifty times. All of these stages are labor intensive and require a prolonged measurement process.
All the above known in the art decisions do not provide for a quickly obtaining accurate measurement results, and are not used for all ranges of pore radii. The process of measurement is a prolonged and laborious one.